JAKARTA (Reuters) - Hundreds of Muslim radicals set two churches ablaze and attacked a court in Indonesia's central Java on Tuesday, calling for harsh punishment for a Christian on trial for blasphemy, police said.

The attacks come two days after a mob beat to death three followers of a minority Islamic sect considered heretical by mainstream Muslims, and at the start of so-called "Inter-faith week", when the country is supposed to celebrate its pluralistic heritage.

The incidents could heighten risk concerns for foreign investors counting on improved religious tolerance in southeast Asia's largest economy, a predominantly moderate Muslim country that is officially secular.

Rights groups and some analysts say a decree passed in 2008 by President Susilo Bambang Yudhoyono's cabinet as he sought the support of influential Muslim groups has actually weakened inter-faith harmony because the law is ambiguous.

On Tuesday, hundreds of men -- many wearing Muslim prayer caps or scarves -- hurled rocks at a court building in Temanggung, around 400 km (250 miles) from the capital, Jakarta, as it heard prosecutors demand a five-year jail term for a Catholic man accused of distributing blasphemous material.

They also pelted riot police with rocks and other missiles before attacking three churches, setting on fire two of them as well as a police truck, said Djihartono, a Central Java police spokesman.

PRIEST BEATEN UP

A priest in Temanggung saw his church being burned, the windows trashed by the mob, said Windyatmoko Bernardus, a Catholic priest in a nearby town who is a member of the same order.

"My friend was beaten up by the mob before being rescued and taken to a military post," Bernardus said.

Djihartono said that police, with back-up from the army, were guarding the town, adding the situation was gradually returning to normal.

Police also said on Tuesday they had arrested two suspects in connection with the mob attack on followers of the Ahmadi movement that was captured by dozens of cameras and distributed by local media and social network sites.

The footage showed the Ahmadi followers apparently being bludgeoned to death while heavily outnumbered police watched from the sidelines.

The Ahmadis believe Mohammad was not Islam's final prophet and say Mirza Ghulam Ahmad, who founded the sect in India in the 19th century, was a successor and messiah.

Only six religions or beliefs are officially recognised in Indonesia -- Islam, Protestant and Catholic Christianity, Hinduism, Buddhism and Confucianism.

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